U.S. patent application number 15/807755 was filed with the patent office on 2018-03-08 for operation of control protocol data units in packet data convergence protocol.
The applicant listed for this patent is InterDigital Patent Holdings, Inc.. Invention is credited to Mohammed Sammour, Stephen E. Terry, Peter S. Wang.
Application Number | 20180070227 15/807755 |
Document ID | / |
Family ID | 40526915 |
Filed Date | 2018-03-08 |
United States Patent
Application |
20180070227 |
Kind Code |
A1 |
Wang; Peter S. ; et
al. |
March 8, 2018 |
OPERATION OF CONTROL PROTOCOL DATA UNITS IN PACKET DATA CONVERGENCE
PROTOCOL
Abstract
A method and apparatus reports packet data control protocol
(PDCP) status and PDCP resets in a wireless communication, using
control PDUs that may have security protection applied by ciphering
of the control PDUs. Reliability of the PDCP status and reset
messages may be assured by acknowledgement according to an
acknowledged mode or to an unacknowledged mode.
Inventors: |
Wang; Peter S.; (E.
Setauket, NY) ; Terry; Stephen E.; (Northport,
NY) ; Sammour; Mohammed; (Alrabieh-Amman,
JO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
InterDigital Patent Holdings, Inc. |
Wilmington |
DE |
US |
|
|
Family ID: |
40526915 |
Appl. No.: |
15/807755 |
Filed: |
November 9, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13676366 |
Nov 14, 2012 |
9843925 |
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15807755 |
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12238810 |
Sep 26, 2008 |
8335189 |
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13676366 |
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60976139 |
Sep 28, 2007 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 12/0017 20190101;
H04W 80/02 20130101; H04L 63/0428 20130101; H04W 12/1008 20190101;
H04W 12/1006 20190101; H04W 8/30 20130101 |
International
Class: |
H04W 8/30 20090101
H04W008/30; H04W 12/02 20090101 H04W012/02; H04W 80/02 20090101
H04W080/02 |
Claims
1. A method for ensuring delivery of packet data convergence
protocol (PDCP) packets in a wireless communication, the method
comprising: performing re-establishment of a PDCP entity responsive
to a handover error, wherein performing re-establishment of the
PDCP entity comprises resetting a header compression entity;
generating a PDCP-STATUS message based on the re-establishment of
the PDCP entity, wherein the PDCP-STATUS message comprises a
starting sequence number and a bitmap, wherein the starting
sequence number is a sequence number of a PDCP service data unit
(SDU) that has not been successfully received by a peer entity and
wherein the bitmap comprises a plurality of bits, each of the
plurality of bits representing a status of a PDCP SDU, and the
bitmap does not include a bit that represents a status of the PDCP
SDU associated with the starting sequence number; sending the
generated PDCP-STATUS message to the peer entity in a PDCP control
packet data unit (PDU); and receiving a retransmission of the PDCP
SDU associated with the starting sequence number and at least one
of any other PDCP SDU based on the at least one of any other PDCP
SDU being negatively acknowledged via the bitmap.
2. The method of claim 1, wherein the generating of the PDCP-STATUS
message based on the re-establishment of the PDCP entity is
configured by a radio resource control (RRC) signal.
3. The method of claim 1, wherein re-establishing the PDCP entity
comprises at least one of the following: resetting or
re-establishing security operations or security parameters to at
least one of the following: last configured values, initialized
security parameter values; or past setting/configuration values
indexed by a reset parameter; resetting or re-establishing a PDCP
sequence number to zero; or resetting or re-establishing PDCP
reordering parameters for in-sequence-delivery or duplication
detection operations.
4. The method of claim 3, wherein the re-establishing of the PDCP
entity is triggered by an indication from an RRC layer.
5. The method of claim 1, further comprising: receiving a handover
command; and sending a subsequent PDCP-STATUS message based on the
received handover command.
6. The method of claim 5, wherein the handover command is received
in a radio resource control (RRC) message.
7. The method of claim 1, further comprising, after resetting the
header compression entity, receiving a subsequent packet using full
header information.
8. The method of claim 1, wherein the full header information
comprises at least a full user datagram protocol (UDP) header.
9. The method of claim 1, further comprising reporting a buffer
status, wherein the buffer status is included in a PDCP control
PDU.
10. The method of claim 1, wherein a first bit of the bitmap
represents a status of a PDCP SDU with a sequence number that is a
next consecutive sequence number following the starting sequence
number.
11. A network node comprising: a transmitter; a receiver; and a
processor, coupled to the transmitter and the receiver, the
processor configured to: perform re-establishment of a PDCP entity
responsive to a handover error, wherein performing re-establishment
of the PDCP entity comprises resetting a header compression entity;
generate a PDCP-STATUS message based on the re-establishment of the
PDCP entity, wherein the PDCP-STATUS message comprises a starting
sequence number and a bitmap, wherein the starting sequence number
is a sequence number of a PDCP service data unit (SDU) that has not
been successfully received by a peer entity and wherein the bitmap
comprises a plurality of bits, each of the plurality of bits
representing a status of a PDCP SDU, and the bitmap does not
include a bit that represents a status of the PDCP SDU associated
with the starting sequence number; the transmitter configured to
send the PDCP-STATUS message to the peer entity in a PDCP control
packet data unit (PDU); and the receiver configured to receive a
retransmission of the PDCP SDU associated with the starting
sequence number and at least one of any other PDCP SDU based on the
at least one of any other PDCP SDU being negatively acknowledged
via the bitmap.
12. The network node of claim 11, wherein the generating of the
PDCP-STATUS message based on the re-establishment of the PDCP
entity is configured by a radio resource control (RRC) signal.
13. The network node of claim 11, wherein: the receiver is
configured to receive a handover command; and the transmitter is
configured to send a subsequent PDCP-STATUS message based on the
received handover command.
14. A network node comprising: a transmitter; a receiver; and a
processor, coupled to the transmitter and the receiver, the
processor configured to perform re-establishment of a packet data
convergence protocol (PDCP) entity responsive to a handover error,
wherein performing re-establishment of the PDCP entity comprises
resetting a header compression entity; the receiver configured to
receive a PDCP STATUS message from a peer entity, wherein the
PDCP-STATUS message comprises a starting sequence number and a
bitmap, wherein the starting sequence number is a sequence number
of a PDCP service data unit (SDU) that has not been successfully
received by the peer entity, and wherein the bitmap comprises a
plurality of bits, each of the plurality of bits representing a
status of a PDCP SDU, and the bitmap does not include a bit that
represents a status of the PDCP SDU associated with the starting
sequence number; and the transmitter configured to retransmit the
PDCP SDU associated with the starting sequence number and at least
one of any other PDCP SDU based on the at least one of any other
PDCP SDU being negatively acknowledged via the bitmap.
15. The network node of claim 14, wherein the PDCP-STATUS message
is included in a PDCP control protocol data unit (PDU).
16. The network node of claim 14, wherein the PDCP-STATUS message
indicates a delivery status of PDCP SDUs transmitted to the peer
entity.
17. The network node of claim 14, wherein the processor is further
configured to manage a PDCP SDU buffer based on the received
PDCP-STATUS message.
18. The network node of claim 17, wherein the processor is
configured to manage the PDCP SDU buffer by removing one or more
PDCP SDUs from the PDCP SDU buffer.
19. The network node of claim 14, wherein the processor is further
configured to report a buffer status, wherein the buffer status is
included in a PDCP control protocol data unit (PDU).
20. The network node of claim 14, wherein a first bit of the bitmap
represents a status of a PDCP SDU with a sequence number that is a
next consecutive sequence number following the starting sequence
number.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. patent
application Ser. No. 13/676,366 filed on Nov. 14, 2012, which is a
Continuation of U.S. patent application Ser. No. 12/238,810 filed
on Sep. 26, 2008, now U.S. Pat. No. 8,335,189, which claims the
benefit of U.S. Provisional Patent Application No. 60/976,139 filed
on Sep. 28, 2007, the contents of each of which being incorporated
by reference as if fully set forth herein.
FIELD OF INVENTION
[0002] The present invention is related to wireless
communications.
BACKGROUND
[0003] Current effort for the Third Generation Partnership Project
(3GPP) Long Term Evolution (LTE) program is to bring new
technology, new architecture and new methods in the new LTE
settings and configurations in order to provide improved spectral
efficiency, reduced latency, better utilizing the radio resource to
bring faster user experiences and richer applications and services
with less cost.
[0004] LTE packet data convergence protocol (PDCP) is now
responsible for ciphering, integrity protection and PDCP service
data unit (SDU) sequence number (SN) maintenance. While PDCP Data
protocol data units (PDUs) are ciphered, LTE specifications do not
allow for ciphering and integrity protection of PDCP Control
PDUs.
[0005] Peer PDCP entities can exchange PDCP-STATUS messages, for
instance during a handover. A PDCP-STATUS message indicates whether
or not one or more PDCP SDUs has been received by the receiving
PDCP entity (i.e. it provides positive or negative acknowledgements
for PDCP SDU SN(s)). A PDCP-STATUS message may be sent using a PDCP
Control PDU.
[0006] PDCP operations have already evolved beyond the previous
Universal Mobile Telecommunication Systems (UMTS) realm. As a
result, PDCP Control PDUs are available to assist special
operations as well as to regulate the normal operation management
tasks. To this end, the PDCP Control PDU operations need to be
defined and standardized in order to coordinate the actions between
the peer PDCP entities.
SUMMARY
[0007] A method and apparatus report packet data control protocol
(PDCP) status and PDCP resets in a wireless communication, using
control PDUs that may be have security protection applied by
ciphering of the control PDUs. Reliability of the PDCP status and
reset messages may be assured by acknowledgment according to an
acknowledged mode or an unacknowledged mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] A more detailed understanding may be had from the following
description, given by way of example in conjunction with the
accompanying drawings wherein:
[0009] FIG. 1 shows block diagram of a PDCP layer with ciphering
and integrity protection functional entities;
[0010] FIGS. 2A and 2B show signaling diagrams for uplink and
downlink protocol status messages, respectively, and corresponding
status acknowledgement messages;
[0011] FIGS. 3A and 3B show a PDCP/RLC inter-layer polling
mechanism used for a PDCP-STATUS message reliability check;
[0012] FIG. 4 shows an RRC primitive to trigger a PDCP-STATUS
message;
[0013] FIG. 5 shows a PDCP Polling mechanism for triggering a
PDCP-STATUS message;
[0014] FIGS. 6A and 6B show signaling diagrams for uplink and
downlink protocol reset messages, respectively, and corresponding
reset acknowledgement messages; and
[0015] FIG. 7 illustrates an example PDCP-STATUS message.
DETAILED DESCRIPTION
[0016] When referred to hereafter, the terminology "wireless
transmit/receive unit (WTRU)" includes but is not limited to a user
equipment (UE), a mobile station, a fixed or mobile subscriber
unit, a pager, a cellular telephone, a personal digital assistant
(PDA), a computer, or any other type of user device capable of
operating in a wireless environment. When referred to hereafter,
the terminology "base station" includes but is not limited to a
Node-B, a site controller, an access point (AP), or any other type
of interfacing device capable of operating in a wireless
environment.
[0017] In the present embodiment, PDCP Control PDUs are ciphered at
the PDCP layer whether in the user plane (U-plane) or control plane
(C-plane). Types of PDCP Control PDUs for ciphering include, but
are not limited to PDCP STATUS messages and PDCP RESET messages.
Robust Header Compression (RoHC) feedback packets may be excluded
from the ciphering.
[0018] FIG. 1 shows a block diagram of a PDCP layer 101, processing
C-plane PDCP Control PDUs 102, C-plane PDCP Data PDUs 103, U-plane
PDCP Control PDUs 104, and U-plane PDCP Data PDUs 105. A
ciphering/deciphering entity 110 is used to cipher PDCP PDU
transmissions and decipher PDCP PDU receptions. The
ciphering/deciphering entity 110 may use the same cipher key,
ciphering algorithm, and input parameters for the C-plane PDCP
Control PDUs 102 as used for the C-plane PDCP Data PDUs 103.
Similarly, the U-plane PDCP Control PDUs 104 may have the same
cipher key, ciphering algorithm, and input parameters applied by
the ciphering/deciphering entity 110 as for the U-plane PDCP Data
PDUs 105.
[0019] One possible exception of this sharing includes a ciphering
sequence COUNT. The COUNT value includes a first field having a
hyper-frame number (HFN) and a second field having a PDCP sequence
number (SN), where the SN for the U-plane PDCP Control PDUs 104 may
be a unique sequence compared to that for the U-plane PDCP Data
PDUs 105. Consequently, for a unique SN, the COUNT sequence of the
PDCP Control PDU 104 would be different than the COUNT sequence of
the PDCP Data PDU 105.
[0020] With respect to maintenance of PDCP SNs, the U-plane PDCP
Control PDUs 104 may have a dedicated PDCP SN domain per radio
bearer. The U-plane PDCP Control PDUs 104 may also have a dedicated
HFN or the most significant bits (MSBs) for the COUNT value
construction. The HFN or MSBs of the COUNT value of the PDCP
Control PDU may be initialized mutually in the WTRU and the evolved
UMTS terrestrial radio access network (E-UTRAN). A predefined
initialization rule may be applied to a stored HFN seed value in a
UMTS subscriber identity module (USIM) in the WTRU. The HFN seed
value is taken from running HFNs and saved in the USIM upon
powering down of the WTRU. When the WTRU powers on again, this
stored HFN seed value is taken out to re-initialize the HFNs. This
stored HFN seed value for the PDCP Control PDUs could be the same
or different from the stored value used for PDCP Data PDUs. For
example, the same stored value could be used with a different
initialization rule then being applied to the stored value for the
PDCP Control PDU:
HFN=START+OFFSET.sub.PDCP Control PDU Equation (1)
where START is the stored HFN seed value common to both the PDCP
Control PDU and the PDCP Data PDU.
[0021] Alternatively, the HFN or MSBs of the COUNT value of a
U-plane PDCP Control PDU 104 may be set to zero, or configured by
the E-UTRAN as part of the PDCP configuration or Security Command
Mode setup. Incrementation of the HFN or MSBs of the COUNT value
may be fixed, or applied at the PDU sequence number value
wrap-around. As an example of a wrap-around incrementation,
consider a 10-bit COUNT value, with a 5-bit HFN field concatenated
with a 5-bit SN field, both initialized to zero. The SN increments
with every sent/received PDU, at values from 0 to 1, 2, . . . , 31.
With another PDU, the SN returns to 0, thus at a `wrap-around`, and
the HFN is incremented by one, as a binary carry.
[0022] Returning to FIG. 1, the PDCP layer 101 includes integrity
protection/verification entity 111, which processes C-plane PDCP
Control PDUs 102 according to the same methods used for C-plane
PDCP Data PDUs 103. During transmission of the C-plane Control PDUs
102, the integrity protection entity 111 takes the PDU data bit
stream as input, together with other inputs such as the security
key, the COUNT value of that PDU, and generates a coded word,
referred to as a message authentication code (MAC-I), sent together
with the PDU proper. When receiving the C-plane Control PDUs 102,
the integrity protection/verification entity 111 performs
verification of the PDUs on the MAC-I.
[0023] According to a second embodiment, PDCP-STATUS PDUs are
exchanged in a message between a WTRU and the E-UTRAN. A
PDCP-STATUS message is exchanged between the WTRU and an E-UTRAN
entity (e.g., an enhanced Node-B (eNB)) over a common radio bearer.
Various signaling parameters for a PDCP-STATUS message may be
organized into an LTE information element (IE) and be carried by an
RRC message. Such parameters include the following.
[0024] A parameter for PDCP reordering purposes may be defined by
an initial PDCP-SN and the range of the PDCP reordering window. The
resulting PDCP SNs may be used at a handover of the WTRU between
enhanced Node-Bs (eNBs), i.e., an inter-eNB handover.
[0025] A parameter for general PDCP transmission and retransmission
regulation may be defined by an Acknowledgement (ACK) or negative
acknowledgement (NACK) of PDCP SDUs with their PDCP-SNs. The
ACK/NACK may indicate PDCP-SDUs selectively for a number N of
consecutive packets, with a starting SN number and subsequent
bitmap with each bit for the status of one SDU (i.e. a PDCP-SN). In
the bitmap, the bit value and its semantics could be consistent
with the ACK/NACK attribute in the IE or the bit value in the map
may instead have its own independent representation. In the latter
case, the attribute ACK/NACK is not needed. For example, an IE
containing [NACK, 323, 101001110] is definitive of negative
acknowledgement of SDU packets with SNs 323, 324, 326, 329, 330,
331. Here, a bit value `1` represents a NACK. The bitmap does not
include the starting SDU 323 since it is already explicitly
expressed in the IE. Instead, the bitmap commences at the next SDU
324 up to SDU 332. Thus, the NACKed SDUs including the starting one
are 323, 324 (the first bit and set), 326 (the third bit and set),
329, 330, 331 (the sixth, the seventh and the eighth bits and set.
The other SDUs are not NACKed. As another example, an IE containing
[323, 101001110] represents SDUs with SN 323, 325, 327, 328 and 332
are missing, since a bit value `0` is an indication for an SDU not
correctly received and needing retransmission. Alternatively, the
ACK/NACK may indicate the PDCP SDUs cumulatively for one
homogeneous status (i.e., all ACK or all NACK), with a starting SN
number and the range for the consecutive SDU SNs. For example, an
IE containing [ACK, 256, 6] represents acknowledgement that packets
were received for SDU SNs 256, 257, 258, 259, 260, 261.
[0026] FIG. 7 illustrates an example PDCP-STATUS message. As shown
in FIG. 7, PDCP-STATUS Message 700 may include Starting Sequence
Number 702 and Bitmap 704. Starting Sequence Number 702 may be the
sequence number of a PDCP SDU that has not been successfully
received. Bitmap 704 may indicate whether PDCP SDUs with sequence
numbers that are subsequent to Starting Sequence Number 702 have
been successfully received. For example, if Starting Sequence
Number 702 is 323,Bitmap 704 may indicate whether sequence numbers
324, 325, 326, . . . , SN.sub.N have been successfully received
(where SN.sub.N may be the last sequence number with a
corresponding bit in Bitmap 704).
[0027] An information parameter may be defined to control general
PDCP transmission/retransmission window operations or receive
window operations and their synchronizations. This includes sliding
the window or changing the window range, which may occur when
reordering PDCP packets at handover. This parameter may be defined
as a window range with a starting SN number, either low end or
trailing end, and a range for the remaining SDU SNs. For example,
an IE containing [256, 16] can be used to represent the SDU SN
window [256, 257, 258, . . . , 271].
[0028] The PDCP-STATUS PDUs may also include parameters for general
PDCP security regulation, which may be defined to inform the peer
PDCP entity about LTE security parameter changes occurring at the
PDCP layer. Here, the PDCP-STATUS PDU is used to indicate the
current HFN or MSB of a ciphering sequence COUNT value that is used
for each relevant radio bearer (RB). For example, an IE may be
defined to include an RB-ID and its current downlink HFN or MSB of
the COUNT value and/or uplink HFN or MSB of the COUNT value.
Specifically, an IE containing [5 and 452/423] can be used to
indicate that a downlink HFN 452 and an uplink HFN 423 for RB-ID 5
need to be reset to at the reception of the STATUS PDU.
[0029] The PDCP-STATUS PDUs can also be used to regulate PDCP SDU
transmission/retransmission and manage SDU buffer spaces.
[0030] The PDCP-STATUS PDUs may also carry parameters to inform,
check and possibly change LTE security operations performed at the
PDCP level if the relevant IE is included in the transmitted
PDCP-Status PDU. The presence of such an IE in the message
indicates a reset of the HFNs for a particular RB.
[0031] FIGS. 2A and 2B show signaling diagrams for the PDCP-STATUS
message PDUs. In FIG. 2A, the WTRU sends a PDCP-STATUS message 201
to the eNB. For reliability control, the WTRU receives a
PDCP-STATUS ACK signal 202 from the eNB to acknowledge that the
PDCP-STATUS message was safely received at the eNB. In FIG. 2B, the
eNB sends a PDCP-STATUS message 203 to the WTRU. For reliability
control, the eNB receives a PDCP-STATUS ACK signal 204 from the
WTRU to acknowledge that the PDCP-STATUS message was safely
received at the WTRU. The PDCP-STATUS-ACK message 202, 204 could
either be a dedicated acknowledgement message or be a message that
also contains all other possible PDCP-STATUS parameters.
Alternatively, an acknowledgment could be received as an indication
(acknowledgement on a PDCP-SN or a shorter transaction-Id) in a
PDCP-STATUS message.
[0032] Alternatively, the PDCP-STATUS signaling may be performed
without requiring a PDCP-STATUS ACK signal. The reliability of
PDCP-STATUS message 201, 203 can still be ensured as follows. If
radio link control acknowledged mode (RLC-AM) is the link mode, the
WTRU or eNB can internally check its radio link control (RLC)
status. Alternatively, for all RLC link modes, the WTRU can check a
hybrid automatic repeat request status (HARQ-status) through the
RLC layer, using an internal PDCP/RLC inter-layer polling
mechanism. FIG. 3A shows an example for the RLC-AM link mode, where
a PDCP layer 310 interfaces with an AM RLC layer 320. A PDCP/RLC
inter-layer polling mechanism 301 performs an internal reliability
status check of the RLC layer 320 by setting a polling signal
RLC-DATA-REQ 302, which may include an RB-ID, a data field and an
acknowledgment request, sent from the PDCP layer 310 to the RLC
layer 320. The RLC 320 sets one or more bits of a polling flag 304
on the RLC data PDU(s) carrying the PDCP-STATUS message, and
receives an RLC status report 305 (i.e., an RLC ACK/NACK report).
The PDCP layer 310 receives the acknowledgment signal RLC-DATA-CNF
307 from the RLC 320, indicating the RB-ID and the ACK/NACK.
[0033] FIG. 3B shows an example of PDCP status signaling for
unacknowledged mode (UM) RLC entities. A PDCP/RLC inter-layer
polling mechanism 301 performs an internal reliability status check
to the RLC 320 and in turn to a MAC 330 for aHARQ 340 processor
status. A polling signal RLC-DATA-REQ 302 is set by the polling
mechanism 301, and sent by PDCP 310 to the RLC 320, which forwards
the polling as signal MAC-DATA-REQ 303. These polling signals 302,
303 include the RB-ID, a data field and an acknowledge request. The
MAC 330 sends a signal HARQ-DATA-REQ 304, as data to the HARQ
processor 340. The HARQ processor 340 status is returned to the
PDCP 310 via a HARQ ACK/NACK signal 305, a MAC-DATA-CNF signal 306
as an ACK/NACK, and a RLC-DATA-CNF signal 307 with the ACK/NACK and
the RB-ID. While the above example implementations are described
with reference to a WTRU, the signaling according to FIGS. 3A and
3B could be applied to similar respective entities in an eNB
implementation.
[0034] The PDCP-STATUS message 201, 203 shown in FIGS. 2A, 2B may
be triggered by any of the following triggers.
[0035] At a handover of the WTRU, a radio resource control (RRC)
handover command or handover confirm signal or an RLC Reset
indication may trigger a PDCP-STATUS message 201, 203. This also
includes a new handover occurring while an existing handover PDCP
procedure is ongoing. As shown in FIG. 4, a primitive or signal or
indication 401 from an RRC entity 410 to a PDCP entity 411 of the
WTRU or eNB can convey/trigger the generation of the PDCP-STATUS
message.
[0036] In the case that a PDCP-STATUS message can also be used
beyond handover management for regular operations control, then the
triggering source of the PDCP-STATUS message transmission may
include any one or combination of the following. A periodic
PDCP-STATUS message from a PDCP entity receiver function may be
used, such as a RRC configured and timer based message. The trigger
may be an event based PDCP-STATUS message, and also RRC configured
(e.g., when the window has advanced n=200 SDUs) from either a
transmit or receive function of a PDCP entity. The trigger may
occur after a certain timeout period, such as a PDCP uplink
retransmission failure. Other triggers include an RLC reset or
re-establishment, an RRC handover or other RRC events, and PDCP
events.
[0037] FIG. 5 shows an example of another possible trigger, which
is a reception of a poll signal from the peer PDCP entity. A
PDCP-STATUS polling mechanism 501 is included in a PDCP layer 510,
such that the transmitting PDCP entity can poll the receiving PDCP
entity for its PDCP status by sending a poll signal 502 to the RLC
layer 511, and then on to the lower layers as poll signal 503 for
transmission. The PDCP polling mechanism 501 may utilize a polling
bit in the PDCP header of a PDCP PDU, or it may utilize a PDCP
Control PDU to be used for polling (e.g., a Control PDU type
defined for polling). When the receiving PDCP entity receives a
packet where the `polling bit` is set, or a PDCP Control PDU that
has the polling type, the generation of PDCP-STATUS PDU is
triggered.
[0038] According to a third embodiment, a PDCP-RESET message is
sent as a peer-to-peer message between PDCP entities of the WTRU
and the eNB over a common radio bearer. The PDCP-RESET message is
used to inform or command the peer entity (WTRU/eNB) that a full or
a partial PDCP reset has occurred or needs to occur. The term `PDCP
reset` is interchangeable herein with a PDCP re-establishment. In
order to distinguish whether the PDCP-RESET is a command or an
information signal, a indicator bit can be defined and transmitted
for such a purpose. For example, such an indicator bit can be set
to 0 as an indication that the PDCP "has reset" and set to `1` to
indicate a command "to reset" the PDCP. Additionally, for the reset
command, a timestamp or a frame number to synchronize the RESET
peer action, may be included with the PDCP-RESET message.
Alternatively, the distinction between an informative reset and a
reset command could be implied from the context (i.e. if the WTRU
sends it, then the WTRU is informing the eNB that the WTRU PDCP was
reset; if the eNB sends it, then eNB is commanding the WTRU to
perform a PDCP reset. It should be noted, however, that whichever
peer entity performs a PDCP reset or re-establishment, the
counterpart peer entity will also reset or re-establish its PDCP
entity as well.
[0039] The PDCP reset or re-establishment may be triggered by any
one or combination of the following: an unrecoverable PDCP
operation error (e.g., a buffer error); a timeout on an unexpected
PDCP-STATUS message acknowledgement; an unrecoverable PDCP security
error detected by either peer entity; a handover event for LTE
non-lossless radio bearer(s), in which case, the COUNT is reset to
zero; an error on a new handover while an old handover procedure
has not yet been completed; an unrecoverable error in the header
compression function and operation; an upper layer intervention or
command, such as from the RRC layer on the C-plane or from the
non-access stratum (NAS) on the U-plane, which requires a reset of
the corresponding PDCP entity; and a lower layer indication from
the RLC layer that requires a corresponding PDCP entity reset. In
the case of the unrecoverable security error, it can be detected by
integrity protection on the C-plane and header decompression on the
U-plane, in which case the PDCP-RESET message could be used between
the WTRU and eNB for resetting the de-synchronized security
parameters. Other triggers include: a PDCP security error detected
by integrity protection error; a handover error; an indication from
an RRC layer which requires a reset or re-establishment of a PDCP
entity; and/or an indication from an RLC layer which requires a
reset or re-establishment of a PDCP entity.
[0040] For a full PDCP reset, all of the following function
operations of the PDCP entity of the WTRU or eNB may be changed to
a pre-defined state or operating values (i.e.,
reset/re-established), which could occur at a certain PDCP-SN or at
an absolute time mark, such as a system frame number (SFN) or a
full or modified standard time representation (e.g., international
GMT) or by the time of the reception of the message: [0041] a
header compression entity and operation state are reset to the
initial state and a full header (IP/TCP or IP/UDP/RTP or IP/xxxx)
will be transmitted and expected to be received after the reset per
the header compression algorithm; [0042] security operations or
security parameters are reset to any of the following: last
configured values; initialized security parameter values; or a
certain past setting/configuration values indexed by a parameter in
the RESET message; examples of security parameters being reset
include the security keys, the HFN or MSB values of the COUNT
parameter, or the FRESH value in integrity protection; [0043] a
PDCP-SN reset is honored only from the E-UTRAN to the LTE WTRU and
the PDCP-SN is either to be reset to a specified value (e.g., an
offset) or to zero. The PDCP-SN on each radio bearer may or may not
be reset; and [0044] PDCP reordering parameters for
in-sequence-delivery or duplication detection operations are reset.
For a partial PDCP reset, less than all of the above described
functions or operations are reset/re-established at the PDCP entity
of the WTRU or eNB.
[0045] FIG. 6A shows a signaling diagram of a WTRU sending a
PDCP-RESET message 601 to an eNB to command its peer PDCP entity in
the eNB to reset, or to inform the eNB that the WTRU PDCP has
performed a full or partial reset. For a PDCP-RESET command message
601, an explicit PDCP-RESET-ACK message 602 is returned to the WTRU
after the PDCP reset at the eNB is completed. This acknowledgment
message 602 is not mandatory if the PDCP-RESET message 601 was not
a reset command. FIG. 6B shows the reverse scenario, in which the
eNB sends a PDCP-RESET message 603 to the WTRU. If the PDCP-RESET
message 603 is a command, the WTRU sends an explicit PDCP-RESET-ACK
message 604 after its PDCP has been reset to the command from the
eNB. However, if the PDCP-RESET message 603 is to inform the WTRU
that the eNB performed a PDCP reset, then the PDCP-RESET-ACK
message 604 is not mandatory.
[0046] The PDCP-RESET-ACK message may be defined using a new type
of PDCP Control PDU (e.g., via a `PDU type` field or a `super-field
(SUFI) type` field). As with the PDCP-STATUS message, the
PDCP-RESET acknowledgment signaling can be demonstrated with
reference to FIGS. 3A and 3B. As shown in FIG. 3A, a PDCP/RLC
inter-layer polling mechanism 301 performs an internal reliability
status check of the RLC layer 320 by setting a polling signal
RLC-DATA-REQ 302, which may include a RB-ID, a data field and an
acknowledgment request, sent from the PDCP layer 310 to the RLC
layer 320. The RLC 320 sets one or more bits of a polling flag 304
on the RLC data PDU(s) carrying the PDCP-RESET message, and
receives an RLC status report 305 (i.e., an RLC ACK/NACK report).
The PDCP layer 310 receives the acknowledgment signal RLC-DATA-CNF
307 from the RLC 320, indicating the RB-ID and the ACK/NACK.
[0047] Alternatively, for UM RLC entities, the PDCP entity sending
the PDCP-RESET may utilize a polling mechanism to obtain
acknowledgement indication (e.g., a delivery notification) from the
HARQ entity below the RLC, (i.e., to poll the HARQ transmission
status via RLC and MAC. Or the RLC below the sending PDCP can use
the RLC peer entity acknowledgement to know if the PDCP-RESET
message sent has reached its destination or not. As shown in FIG.
3B, a PDCP/RLC inter-layer polling mechanism 301 performs an
internal reliability status check to the RLC 320 and in turn to a
MAC 330 for aHARQ 340 processor status. A polling signal
RLC-DATA-REQ 302 is set by the polling mechanism 301, and sent by
PDCP 310 to the RLC 320, which forwards the polling as signal
MAC-DATA-REQ 303. These polling signals 302, 303 include the RB-ID,
a data field and an acknowledge request. The MAC 330 sends a signal
HARQ-DATA-REQ 304, as data to the HARQ processor 340. The HARQ
processor 340 status is returned to the PDCP 310 via a HARQ
ACK/NACK signal 305, a MAC-DATA-CNF signal 306 as an ACK/NACK, and
a RLC-DATA-CNF signal 307 with the ACK/NACK and the RB-ID. While
the above example implementations of PDCP-RESET message
acknowledgment are described with reference to a WTRU, the
signaling according to FIGS. 3A and 3B may be applied to similar
respective entities in an eNB implementation.
[0048] While a PDCP reset/re-establishment has been described above
in reference to an explicit PDCP-RESET message, the information
related to inform or command the peer entity (eNB/WTRU) that a full
or a partial PDCP reset has occurred or needs to occur may
alternatively be carried or organized into an LTE information
element (IE) and be carried by an RRC message.
[0049] In another embodiment, an additional type of PDCP Control
PDU is utilized in a PDCP-BUFFER-STATUS message, which describes
the status of the PDCP buffer at the PDCP entity. For example, the
receiving PDCP entity can use the PDCP- BUFFER-STATUS message to
report on the amount of data that is stored in the receive PDCP
buffer (i.e. PDCP buffer occupancy), such as the number of packets
(SDUs) or number of bytes utilized in the receive buffer. This
information is sent from the receiving PDCP entity (WTRU/eNB) to
the transmitting PDCP entity (WTRU/eNB) in a PDCP-BUFFER-STATUS
message, and can be used by the transmitting PDCP entity to affect
its various functions. Similarly, a PDCP-BUFFER-STATUS message may
be transmitted from the transmitting PDCP entity to the receiving
PDCP entity to report on the PDCP transmit buffer occupancy.
[0050] Although features and elements are described above in
particular combinations, each feature or element can be used alone
without the other features and elements or in various combinations
with or without other features and elements. The methods or flow
charts provided herein may be implemented in a computer program,
software, or firmware incorporated in a computer-readable storage
medium for execution by a general purpose computer or a processor.
Examples of computer-readable storage mediums include a read only
memory (ROM), a random access memory (RAM), a register, cache
memory, semiconductor memory devices, magnetic media such as
internal hard disks and removable disks, magneto-optical media, and
optical media such as CD-ROM disks, and digital versatile disks
(DVDs).
[0051] Suitable processors include, by way of example, a general
purpose processor, a special purpose processor, a conventional
processor, a digital signal processor (DSP), a plurality of
microprocessors, one or more microprocessors in association with a
DSP core, a controller, a microcontroller, Application Specific
Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)
circuits, any other type of integrated circuit (IC), and/or a state
machine.
[0052] A processor in association with software may be used to
implement a radio frequency transceiver for use in a wireless
transmit receive unit (WTRU), user equipment (UE), terminal, base
station, radio network controller (RNC), or any host computer. The
WTRU may be used in conjunction with modules, implemented in
hardware and/or software, such as a camera, a video camera module,
a videophone, a speakerphone, a vibration device, a speaker, a
microphone, a television transceiver, a hands free headset, a
keyboard, a Bluetooth.RTM. module, a frequency modulated (FM) radio
unit, a liquid crystal display (LCD) display unit, an organic
light-emitting diode (OLED) display unit, a digital music player, a
media player, a video game player module, an Internet browser,
and/or any wireless local area network (WLAN) or Ultra Wide Band
(UWB) module.
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